Stabilized mineral oil



Patented Mar. 10, 1942 UNIED S ATES PATEN OFFICE STABILIZED MINERAL OILPhilip Gordon Colin, Westfield, N. J., assignor to Tide Water AssociatedOil Company, Bayonne, N. J., a corporation of Delaware 3 Claims.

This invention relates to the stabilization of lubricants; and, moreparticularly, is concerned with mineral hydrocarbon lubricating and likeoils having incorporated therewith substances or compounds efiective toinhibit or retard deterioration in service.

The useful service life of mineral oils, in respect both of thecharacter and rapidity of deterioration, is influenced by the serviceconditions obtaining during use. In some instances,,as in thelubrication of internal combustion engines, high temperatures prevailand thin films of the oil are in continued and renewed contact with hotmetal surfaces. Strongly oxidizing atmospheres may be encountered inother services where operating temperatures are the same or may belower. In the lubrication of steam turbines, the oil temperature isrelatively low but contacted metal surfaces or other operatingconditions may catalyze, promote or permit acid or sludge formation witheventual emulsification due to the presence of water. For transformer,cable wrapping or other electrical services, the foregoing or otherfactors may tend to occasion deterioration.

Petroleum hydrocarbon oils may be improved in some respects by refiningmethods effective to remove or convert, at least in part, certaindeterioration inducing constituents normally present therein. Refiningwith chemicals frequently is employed, as by extraction with selectivesolvents of the character of phenol, liquid sulfur dioxide,nitro-benzine, furfural, and others well known in the art as well ascombinations thereof, by clay filtration, or by moderate treatment withsulfuric acid of less than fuming acid strength. More drastic refining,as by treatment with fuming sulfuric acid, may be resorted to when it isdesired to produce high refined viscous hydrocarbon oils (the so-calledtechnical white oils) from which substantially all asphalticconstituents have been removed. The refined products, however, still areto an undesirable degree susceptible to oxidation, polymerization, orother chemical phenomena to which may be attributed observed impairmentof the oil resulting from or indicated therewith of substances orcompounds having an.

inhibiting or retarding action in one or another respect upon thedeterioration of the oil. Many suggestions heretofore have been made inthis direction and a number of compounds advanced for trial asinhibitors some of which in greater or less degree have provedeffective. Discrepancies in results have been noted, however, both as tothe relative inhibiting effect of a given compound with different oilsin overcoming a particular undesired result, and as to the eifectivenessof a given inhibitor in preventing difierent undesired results flowingfrom the same or different service uses of a given oil. Analogy betweendifferent petroleum products and the efiective inhibiting action ofvarious compounds therein does not seem to exist in suflicient degree toprovide a reliable basis for predicting the value of an inhibitor in oneoil environment from its efiect in another. Thus, many compoundsefiective as anti-gum forming agents for cracked gasoline may be whollywithout effect in petroleum lubricating oils. Again, certain inhibitorsof value in preventing deterioration of very highly refined turbine oils(the so-rcalled technical white oils) have proved quite ineffective inrespect of inhibiting action in less highly refined turbine oils.

The action of inhibitors, particularly in mineral hydrocarbon oilenvironments, appears, therefore, to be in a sense specific not only forcertain reactions but further with respect to the character of the oil,the nature and extent of the refining to which it has been subjected,and the service for which it is intended. The present invention isconcerned with and provides a compound of proven inhibiting action; butit is deemed undesirable and of little practical value to attempt orrely upon any prescribed theory in explanation of observed eifects orresults.

In its broad aspect, the present invention relates to the use of aninhibitor which I have discovered to be of marked utility in preventingthe deterioration of viscous or relatively viscous petroleum oils (ascontrasted with the less viscous or non-viscous distillate petroleumproducts such as gasoline and kerosene).

More specifically, an important object of the invention is to provide aneffective inhibitor for lubricating and like oils of petroleum origin;which oils have been subjected in greater or less degree to conventionalmethods of refining other than drastic treatment of the characterresorted to for the production of water white viscous mineral oils (viz:technical white oils as prepared by extended treatment with heavy fumingsulfuric acid).

A further object of the invention is to provide, for the indicated use,an inhibitor compnsing dialpha. naphthylamine. It is likewise an objectof the invention to improve, and to provide improved, lubricating oilsby incorporating therewith small amounts of di-alpha naphthylamine.

Other objects and advantages will appear from the following descriptionof the invention and the illustrative examples presented hereinafter inorder that the invention may be more particularly ascertained.

Various tests have been devised and are available by which a comparativeevaluation of oils with respect to deterioration thereof in service maybe obtained in a relatively short period of time. Some of these testsare of longer duration than others, but have the advantage of affordinga, perhaps more reliable laboratory criterion by which to judge therelative value of various inhibitors than extremely accelerated tests.

One such relatively prolonged test, which has proved of particularconvenience in, although not limited to, the evaluation of oils intendedfor such service as the lubrication of steam turbines, is the familiarFunk test. In this test, a measured quantity of oil and water(ordinarily 8 gallons of oil and 0.8 gallon of distilled water) iscontinuously circulated through a cast iron chamber under conditions ofviolent. agitation, the oil being maintained at a temperature of 200 F.and air being passed continuously through the oil asit circulates andre-circulates through the chamber. The length of time required to form1% (by volume) of sludge and emulsion as measured in a centrifugedsample is the criterion by which the relative service life of the oil ismeasured.

Di-alpha naphthylamine is a compound con-' forming to the structuralformula:

and may be prepared, for example, by reacting Funk machine as anevaluating means, clearly demonstrate the efficacy of di-alphanaphthylamine as an inhibitor of deterioration in viscous mineralhydrocarbon oils. The runs were made with a turbine oil, produced froman East Texas crude petroleum, which oil had been refined by solventextraction with liquid sulfur dioxide and had a viscosity at 100 F. of150 Saybolt seconds.

Time to form Inhibitor 1% sludge and emulsion Hours None 50 0.05%di-alpha naphthylamine 2100+* *No evidence of sludge and emulsionformation at 2100 hours.

A particular advantage of the inhibitor according to the inventionresides in the extremely small proportions necessary to efiect verysubstantial inhibiting or stabilizing of the oil in respect ofdeterioration thereof. This is aptly demonstrated by the foregong datawherein 0,05% or di=alpha naphthylamine is shown to occasion aremarkable increase in the Funk life of the oil in question. It will beunderstood, of course, that larger or smaller proportions of inhibitormay be used as deemed desired, but in general it is contemplated thatthe practice of the invention will entail the use of amounts of theorder of less than 1% and, in the interests of economy, less than 0.1%.My investigations indicate that the potency of this inhibitor is suchthat proportions in the range of 0.005% to 0.05% will in many cases beentirely satisfactory.

The compound which I have discovered to be of value as an inhibitor forlubricating and like petroleum oils is readily soluble in the oil inproportions well in excess of the range indicated above as givingeffective stabilizing action. The invention may be practiced, therefore,either by the direct addition of inhibitor to oil'in the desiredinhibiting proporton or, as mayin many instances be preferable, bypreparing a more concentrated solution of inhibitor in oil andthenadding a suitable amount of such concentrate to bulk quantities of oil.

The use of di-alph naphthylamine as an inhibitor according to theinvention is not confined to the specific oil designated in theforegoing example. Other mineral hydrocarbon oils of lubricating oilcharacter may be stabilized against deterioration by the incorporationtherewith of this inhibiting compound. Thus, the inhibitor of theinvention may be applied to the stabilization of oils having greater orless viscosity than 150 seconds Saybolt at F.; and to such oils asrefined by various methods alternativeto extraction with liquid sulfurdioxide. However, the use of this inhibitor in technical white oilsderived from petroleum as by drastic refining with fuming sulfuric acidforms no part of the present invention; nor does the present tain otherservices where the deterioration in question primarily is one caused bythe oil rather than of the oil itself. A particular example of this hasbeen noted in connection with studies of the effect of various mineralhydrocarbon lubricating oils upon the corrosive deterioration of certainhard bearing alloys such as cadmium-silver, cadmium-nickel andcopper-lead, now frequently employed in automotive services in lieu ofthe softer Babbitt bearings.

One difliculty which arose early in the use of these new type bearingswas the very rapid corrosion thereof by many lubricating oils; and onemethod of retarding or preventing such corrosion is to incorporatesuitable inhibitors in the motor oil.

In the hope that the very unusual inhibiting action of di-alphanaphthylamine in turbine oil and like service was an indication thatthis compound likewise would be of value as a bearing corrisioninhibitor, tests were made using cadmium-silver, cadmium-nickel andcopper-lead bearings. The results, however, were quite negative, nomeasurable improvement or degree of bearing corrosion inhibition beingproduced.

It would appear, therefore,that the compound comprising the inhibitor ofthe present invention, While remarkably effective in preventing theserv- 'ice deterioration of certain viscous hydrocarbon oils, is clearlyspecific in its action.

This application is a substitute for my application Serial No. 137,012,filed April 15, 1937, and now abandoned.

I claim:

1. Mineral oil composition comprising'a viscous hydrocarbon oil normallytending to deteriorate

